Tuning device for radio sets



Jan. 12, 1937. E. c. BOOTH 2,057,871

Y TUNING DEVICE FOR RADIO SETS Fild Aug.r15, 1935 alliez/www Patented Jan. l2, i937 STATES y PATENT orties TNNG DEVICE FOR RADIO SETS Application August 15, 1935, Serial No. 36,299

2 Claims.

My invention relates to the tuning of a radio receiving set and particularly to that type of set designated as all wave. In such sets, it is customary to employ the same tuning unit, usually variable condensers, for tuning the set within the limits of each frequency band and to employ switch mechanism for changing the band of frequencies over which the set may be tuned by the tuning unit. The device employed for indicating the setting of the set usually comprises a dial which is angularly adjustable with the movable elements of the tuning condensers and which bears one scale for each band of frequencies which the set is adapted to receive.

It is the object of my invention to produce a tuning and indicating device for an "all wave radio receiver whichwill have advantages over devices previously in use. More specifically, it is my object to produce a device in which the exceedingly fine adjustments necessary for the satisfactory reception of extremely high frequencies may be easily made and accurately indicated. A further object of my invention is to produce an adjusting and indicating device which may be simply and economically constructed and which will have a wide application.

In carrying out my invention, I mount on the adjusting shaft of the tuning condensers a dial carrying a plurality of scales co-extensive in circumferential extent and radially displaced from each other. In rear of this dial I place a lamp; and between the lamp and dial I mount a stationary mask having a narrow radial slot through which light may pass to dei-lne an index on the surface of the translucent dial. Between this stationary mask and the dial I provide an angularly adjustable sector which has one opening for each scale on the dial, such openings being radially spaced inaccordance with the radial spacing of the scales on the dial and also being angularly staggered so that they can successively be brought into alinement with the slot in the stationary mask. The sector is operatively connected to the band selector switch of the radioreceiving set so that the setting of the sector will be coordinated with that of the switch to illuminate only that dial-scale which is used for adjusting the set in the band to which it is made responsive by the band-selector switch.

I prefer to secure adjustments of the condenser shaft through the medium of a speed-reducing device the driven element of which is operatively connected to the condenser shaft through reducing gearing. Preferably, the driven element of the speed-reducing device is provided with a (Cl. 11G-124.4)

desired fashion from the frame I I of the chassis.

The movablev elements of the tuning condensers are fixed to a shaft I2 which extends forwardly and terminates adjacent the rear face of the front walls I3 of the cabinet within which the set is enclosed.

Fixed to the shaft I2 near its front end I provide a disk I5 of transparent material the outer edge of which overlaps and is secured to a ring I6 of translucent material carrying a plurality of graduated scales, here shownv as three in number.

The scales on the dial I6 are illuminated from the rear by a `lamp I'I supported from the frame I I; and between the dial and lamp I mount a stationary mask I8 of translucent material provided with a vertically extending narrow slot I9 1,.. having a length sufficient to embrace all the scales of the dial I6. y

Loosely mounted on the shaft I2 I provide a swingable sector 2| of translucent material having radiallyspacecl and angularly staggered openings 22, 23, and 24, one for each scale on the dial I6, the radial disposition of these openings being such that one of them overlies each of the scales. A link 25 connected to the sector 2| at an eccentric point extends to the outer end of an arm 2E secured to the shaft 2l of the band-selector switch, whereby the setting of the sector 2| will be coordinated with the setting of the bandselector switch. The front wall I3 of the cabinet is provided with an opening in which an escutchecn plate 28 is mounted, such plate having a Window through which the illuminated portion of the dial I6 is visible.

The shaft I2 is conveniently adjusted through a speed reducing drive here shown as consisting of a gear 30 secured to the shaft I2 and meshing with a pinion 3| carried by a stub-shaft 32 which is directly connected with a rotatable sleeve 33 carrying an Vadjusting knob 34. The speed reduction provided by the gearing 30-3I will ordinarily permit sufficiently accurate adjustment of the condensers I for reception in the broadcast band; but the neness of the adjustment thus provided is not adequate to permit'l satisfactory tuning in the higher-frequency bands. I therefore prefer to provide a speed-reducing drive for the pinion 3|.

The speed-reducing drive illustrated in the 4drawing comprises a pair of stamped sheet-metal disks 35 and 36 formed to provide hubs kwhich receive the sleeve 33 and also to provide an outer race for balls 31 mounted in angularly spaced openings in the sleeve 33. Within the sleeve 33 and rotatable relatively thereto is disposed a shaft 38 which is grooved to provided an inner race for the balls 31. held against rotation and are yieldingly forced together, as by a spring 39, to provide for the application of pressure to the balls 31.- When the sleeve 33 is adjusted by rotation of the knob 34 the pinion 3| is driven at the same speed', -but`if the shaft 38 is rotated, as by means of a knob 40 on its outer end, the sleeve 33, and with it the pinion 3|, will be driven at a reduced speed.

To give a more accurate indication of the tuning adjustment than is provided by the scales on the dial I6, I may employ an auxiliary graduated dial 45 rotatable with the, pinion 3| and conveniently secured to the sleeve 33 ahead of the dial I6 where its graduations are visible through a second window 46 in the escutcheon plate 28. An index for the graduations on the dial 45 may be provided by a slit 41 in a translucent mask 48, the slit 41 passing light from a lamp 49 suitably supported from the frame I I of the chassis. Conveniently, the mask 48 is supported from the shaft 21 and sleeve 33, the mask being provided, at its lower end, With a hole closely fitting the shaft 21 and, at an intermediate point, with a vertically elongated slot which receivesA the sleeve 33. The purpose of elongating vertically the opening which receivesthe sleeve 33 is to accommodate for different spacings of the shaft 21 and sleeve 33.

Conveniently, the mask I9 and the* lamps I1 and 49 are supported from a sheet-metal bracket 55, the two lamps I1 and 49 being located respectively above and below such bracket. so that light from the lamp I1 will be prevented from striking the dial 45 and llight from the lamp 49 will be prevented from striking the dial I6.4

In the arrangement illustrated in thedrawing, light emitted by the lamp 49and falling on the dial 45 must pass through the swinging sector 2|; and to prevent the interruption of too much light by this sector, it is provided with an arcuate slot 56 having a sucient angular extent to prevent interference with light from .the lamp` 49 throughout the entire range of sector movement. Light from the lamp 49 illuminating the dial `45 The disks 35 and 36 are` lar extent not to interfere with movement of the dial I6 throughout its entire range of adjustment.

In the operation of the tuning device described above, the band-selector switch is adjusted under the control of the shaft 21 to adapt the set for the reception of the desired band of signals. This setting of the selector switch automatically places the sector 2| in position so that the proper scale on the dial I6 will be illuminated by light passing through one of the openings 22, 23, or 24. 'I'he tuning condensers I0 are then roughly adjusted by rotation of the knob 34; and if a finer adjustment is necessary, it may be secured by manipulation of the knob 40. Because of the speed-reducing connection provided by the gears 30 and 3| between the condenser shaft I2 and the sleeve 33, a very accurate indication of the condenser-setting may be obtained by reading both the dial I6 and the dial 45.

I claim as my invention:

l. Control means for a radio receiving set having a tuning device provided with a rotatably adjustable tuning element, a graduated dial mounted on said tuning element for rotation therewith, a speed-reducing mechanism having rotatable driving and driven members, reduction gearing operatively interconnecting said driven member with said tuning element, a second graduated dial rotatable with said driven element, and a control knob rotatable with each of said driving and driven elements and accessible for manual manipulation.

2. Control means for a radio receiving set having a tuning device provided with a Vrotatably adjustable tuning element, a graduated dial mounted on said tuning element for rotation therewith, a rotatable member, said dial being provided with an arcuate slot through which said rotatable member extends, speed-reducing gearing operatively interconnecting said rotatable member and tuning element, a second graduated dial mounted on and rotatable with said rotatable member, said rst named dial having a transparent central portion overlapped by saidv 

